So looking at one example as I'm sure the root cause is the same, the buttons in toolbar not showing all the time. Is this reproducible in a small test case? I know you said it's random but does it happen in a small test?

I've been using the nightly builds and I can say that, at least for me, the issue with Chrome 18/19, was resolved on the latests builds of Feb. I don't know which build was beta3 based on... (haven't used the official releases sin the nightly builds are available)

The problem with toolbar buttons "disappearing" (the markup is there but the width was set to 0px) and grid columns losing its "flex" (the columns where shrinking to the left), and the problem with charts legend stuck on the upper left, where happening constantly on my end... and I also could reproduce then toolbar/grid problems on the theme example of the different builds.... (it was a matter of resizing the window just a few times, sorting on some grids, or resizing a panel a few times... sometimes it happened on the first window resize, sometimes it happened after a lot of tries, it was a really rare and random bug...)

I had to move to chrome stable (still using it), but now I'm constantly testing with google canary, so, at least with the builds from the 27-28 of Feb and Canary (19.0.1064.0 canary) the problem seems to be fixed.

I will try to find time and test with the 18 builds during the weekend and see if I can reproduce the problems with the nightly builds...

All my apps are now running on 4.1, and I'm pretty happy with it...

I've been downloading the nightly builds daily and kdiff'ing them..., sometimes I had to do a few overrides (like the one on the file input that were rendered as disabled, and a few others).. now I just have 3 or 4 overrides (that's even less that what I had on 3.x)...

Thanks for your help, you described the same problems I have, but the only difference is the build date. I'm happy to know these problems are not there anymore. Probably these issues have already been fixed in the build you are using.

I'm using the last public beta 3 build:
Build date: 2012-02-21 23:18:31

As I don't have access to the nightly builds (even with commercial license) so I have to wait for a new public release.

This is another example why Sencha should open their bugtracker. I spent hours trying to discover WHAT and IF I was doing something wrong, but in the end it seems it was a bug and has already been fixed.